Method for sizing photographic paper



METHOD FOR SIZING PHOTOGRAPHIC PAPER Filed March 27, 1937 John 6. Tmhey INVENT OR.

BY m. fm

ATTORNEYS Patented Jan. 10, 1939 UNITED STATES PATENT OFFICE 2,143,809 Marnon FOR srzmc. rno'roonarmo PAPER Application March 27,

5 Claims.

This invention relates to paper making and particularly to a method of sizing paper. One object of my invention is to provide a method of sizing paper by which the amount of size applied to the paper may be accurately controlled. Another object of my invention is to provide a method of sizing by means of condensable and non-condensable gases, these gases being mixed in. definite proportions for different sizing requirements. Another object of my invention is to provide a continuous method of sizing strips of paper rapidly and for controlling the amount of size taken up by the paper without necessarily altering the viscosity of the sizing solution. Still another object of my invention is to provide a method of sizing paper which can be readily carried out by relatively inexperienced operators and other objects will appear from the following specification, the novel features being particularly pointed out in the claims at the end thereof.

In the past, sizing has been one of the more diflicult steps in paper making because it has always been difficult to force a very large amount of sizing into the paper and it has been also difficult to control the exact amount of size taken up by the paper. The ordinary tub sizing sizes paper sufflciently for some purposes where it is desirable to have a comparatively small amount of size taken up by the paper and to have this size applied primarily to the surfaces of the sheet.

In Patent No. 2,059,880, Lane, for Method of sizing photographic paper", granted November 3,

1936,-a method of sizing paper utilizing a steam blast is described and this method has been successful in that s r-large amount of size can be readily applied to paper passing through the machine at a normal rate of speed. However, in this patent, the sizing is primarily controlled by the volume and velocity of the steam used and the viscosity of the sizingsolution. By cutting down the quantity of steam, the amount of size taken up by the paper can be controlled within certain limits but it is my intention to improve on the method shown in the Lane patent by providing a method by which a far greater range ofcontrol is possible. ,With the method 1 which will be hereinafter described, I can size paper with an extremely small quantity of size 1937, Serial No. 133,422

To accomplish this, I mix condensable and noncondensable gases in varying proportions and treat the paper with the mixed gases immediately before passing it through the sizing bath and the proportions of the mixture control the sizing operation. This can be further controlled by the viscosity of the sizing solution but I have found it more convenient to use a sizing bath-of approximately the same viscosity all of the time and to use steam with various proportions of hot air mixed therewith to determine the amount of size taken up by the paper. V

I have shown in the drawing one way of carrying out my method and this will now be described.

In the drawing wherein like reference characters. denote like parts throughout, Fig. 1 is a front elevation of an apparatus for delivering mixed gases for treating paper before it passes into a sizing bath. y 2

Fig. 2 is a side elevation of the apparatus shown in Fig. 1, parts being broken away for the sake of clearness.

Fig. 3 is an enlarged'sectional view of an aspirator for mixing the gases.

Fig. 4 is a top plane view of shown in the preceding figures.

In accordance with my invention, I treat the paper coming off the drying rolls of a paper making machine with a mixture of steam and hot air, the velocity of this gaseous mixture being 3 sufflcient to drive out the air in the interstices of the sheet replacing it with the gaseous mix-- ture The paper web is then passed directly through the sizing bath and the amount of size taken up by the sheet depends upon the proportion' of the condensable and non-condensable gases in the sheet and on the viscosity of the sizing solution. As shown in Figs. 1' and 2, I prefer to provide a chest I made in two sections 2 which may be separable down the center 4 so that a sheet of paper indicated at 5 maybe passed over the guide roller 6 between the sections 2 of the chest and over a guide roller 1 as it passes from the chest. It should be noted that the paper inlet 8 lies above the surface 9 of the size 45 ID in the bath H and that the paper exit l2 from the chest I lies beneath the surface 9 of the'size. Thus after the paper has been treated with the gases inthe chest, it is plunged directly into the size. 50

The chest sections 2 are preferably separated a short distance so that the gases are free to escape through the'openings between the sections although these openings are preferably com-- paratively narrow in width-4w Y4", although 65 the apparatus this dimension may be varied quite widely according to the pressure used on the gases.

The gases are admitted to the two chest sections through a series of pipes l3 each controlled by a valve l4 and each connected to a header pipe l5, this header in turn being connected by a flexible pipe Hi to an L-shaped end H on a mixing chamber Hi, this mixing chamber preferably containing an aspirator designated broadly as I9 and shown in Fig. 3.

The steam inlet may consist of a pipe in which there may be steam of from two to four pounds pressure, this pipe leading down to the nozzle 2| of, the aspirator. It should be noted that the steam pressure is given only by way of example and this can be varied widely to suit the particular type of steam chest and to suit the particular machine which is used.

. Air is admitted through a pipe 22 by means of a valve 23 and by means of the sleeve pipe 24. If the valve 23 is open or partially open, steam passing through the nozzle 2| draws in as much air as is permitted by the valve 23 so that the two gases will be thoroughly mixed and will pass together through the headers l5 into the two sections of the gas chest.

The amount of steam admitted to pipe 20 may be controlled by the valve 25.

I prefer to usue warm or hot air as it is preferable to have the air of somewhere near the temperature of the steam although this is not essential. Accordingly I prefer to provide an air intake in the form of a box 26 which is preferably equipped with a suitable air filter 21 such as a glass filter and which is connected to an air heater 28. This heater may consist of a sleeve surrounding a relatively high pressure steam pipe 29 so that the air in the heater 28 is always raised to a comparatively high temperature.

In carrying out my method with the apparatus above described, the paper web 5 maybe threaded over the roller 6 between the open sections 2 of the chest over the roller I and thence over a roller 30 to the usual squeeze rolls at the end of the sizing bath. The sizing solution ill of the desired viscosity is .then placed in the bath H. I have found that a sizing solution which is made of pounds of size to 100 gallons of water is a very suitable solution to use and I prefer to keep the viscosity of the size fixed as this renders the control of the sizing operation much simpler than where sizing baths of varying viscosities are used. It may be, however, frequently necessary,

to produce special effects, to alter the viscosity of the sizing bath.

The machine is then started, steam being admitted through the-valve 25 and the valve 23 being opened to admit a quantity of hot air. As the paper moves through the chest I, the mixture of the condensable and non-condensabie gases is moving at relatively high velocity through the steam chest escaping from the openings between the two sections. This gaseous mixture replaces the air in the sheet and as the sheet passes into the size I 0, the gases are replaced by the size and thus the amount of sizing is determined.

The best way to determine the size taken up by the sheet is to determine the moisture content of the sheet after it leaves the sizing solution.

Accordingly I prefer to remove small samples of the sheet and weigh them in a wet and dry condition and the amount of moisture indicates the amount of size. If, for instance, ithas been found that a moisture content of approximately 35% is desirable, the admission of hot air to the mixer by means of the valve 23 can be adjusted until the tests show a 35% moisture content. It is then not necessary to adjust the machine until it has been found, by taking further samples, that such adjustment is necessary.

I prefer to keep the steam valve 25 set in a definite position and to alter the mixture of gases by changing the air valve 23, since this makes the operation of the device simpler. It is, of course. sometimes necessary to change the steam valve as well as the air valve.

In extreme cases, it may be found necessary to change the viscosity of the sizing solution and alter both the hot air and the steam valves to obtain the desired results but I have found it suflicient for most purposes to utilize the same sizing bath viscosity and same steam pressure and control the amount of size absorbed by the paper web I entirely by altering the air valve.

If it should happen that the moisture content of the paper differs across the width of the sheet, this can be readily determined and corrected. It is customary in taking samples for determining the moisture content to take samples from the center and from the edges of the sheet. If it should be found that the moisture content diflers by plus or minus 1%-as for instance if one edge should indicate a moisture content of 34% and the opposite end for instance should indicate a moisture content of 37%, it is usually possible to correct this by merely altering the valves H which control the admission of the mixed gases to the steam chest.

With the method which I have above described, the paper is treated with a mixture of condensabie I and non-condensabie gases moving at a comparatively high speed. The relative quantities or proportions of hot air mixed with thesteam determine the amount of size taken up by the paper. When a predetermined setting gives a desired result, it may be repeated at will. Immediately after treating the paper with the mixed gases, it is plunged into the sizing bath. In my copending application No. 133,423, filed March 2'7, 1937, I have described and claimed a preferred type of apparatus which may be used for carrying out the method disclosed herein.

I claim:

1. The method of sizing paper which comprises removing a predetermined proportion of the air in the interstices of the paper by submitting the paper to a blast of steam tempered with a controlled quantity of air which has been heated to approximately the temperature of the steam, and imme- I diately plunging the paper so treated directly into a sizing bath.

2. The method of sizing paper which comprises treating paper with high velocity steam after mixing the steam with a predetermined quantity of hot air, excluding all other air from the paper and plunging the treated paper directly into a sizing bath.

3. The method of sizing pa r which comprises treating a continuously moving paper web with high velocity steam, maintaining the volume and even distribution of the steam by adding controlled quantities of hot air thereto while exclud ng other air from the paper, and plunging the paper so treated directly from the steam treatment into a sizing bath.

4. The method of controlling the penetration of size into paper which comprises removing a predetermined amount of air from the interstices of a paper web with a blast of steam, the removal of air being limited by mixing a controlled quantity of mixture of steam and hot air, the ratio of steam to air being controlled so as to permit introduction into the paper of said predetermined amount of size.

JOHN C. TRAHEY. 

